The unloading of large fish, e.g. tuna, from a fishing vessel that has returned to port is a difficult operation that must be carried out as quickly as possible, to decrease dock time and ensure that the fish remain fresh, while treating the fish themselves as gently as possible so they are not spoiled for subsequent use. The classic system is shown in EP 0,549,819 of Valsecchi which requires that the fish be individually attached to grippers or cables that are then lifted up group-wise out of the hold. Such an intermittent procedure entails substantial lost time while requiring loaders to expertly hook up the fish. If a fish is not properly attached it will drop off, getting lost or fouling the mechanism of the conveyor.
U.S. Pat. No. 1,666,995 of Davis proposes an L-shaped conveyor with a vertical depending arm that guides a sling-type conveyor. Fruit can be loaded manually into the slings at the lower end of the depending arm for relatively gentle treatment as it is conveyed first vertically up and then horizontally off to the wharf. Such a system has the disadvantage that it cannot reach into corners of the hold so that the fruit must be brought to the center of the hold for loading. In addition the conveyor is not good for use with fish, as it would quickly foul.
German 2,306,024 assigned to Creusot-Loire describes a rigid one-piece conveyor arm shaped like a somewhat flattened L that can reach into the corners of a hold remote from the wharf, but that cannot get even close to the corners closer to the wharf. U.S. Pat. No. 1,478,812 of Barene and German patent 3,608,116 of Kostrewa show bucket-type coal conveyors that either are L-shaped and rigid or that have a depending arm that is always vertical. These systems are not adapted for use with fish and, once again, cannot get into all the various corners of the hold.